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What... I Sweat, Since When? - Calculating Your Sweat Rate.

And here comes the wind! If you live in Albuquerque, NM as I do, there is one thing that is always a certainty. Thewind, the wind always comes in March and April. If you continue to wait for the perfect day to start your outdoor running and riding, it just isn’t going to happen. So, you might as well lace up and put those wheels to the ground. For those of you who are racing in the Boulder Ironman 2017 event, the bike route has changed. I personally like that it is now three loops. I totally loved the 3 loops that Arizona Ironman has, so it isn’t like 3 loops has never been done.

With the weather beginning to warm up a bit, I thought I would share some tips to answer the question, how much fluids do I need to consume during a race?

Yes, you do sweat, even in the winter months, you sweat, you might not recognize the ice cubes you are dropping. Just kidding. To help you determine how much fluids you should consume, you should start with determining your sweat rate. Oh, and before I go into the details, keep in mind that you should do this calculation over again when conditions change (conditions meaning, your clothes, weather, etc.).

Sweat rate calculations determine how much fluid an athlete should consume during a training session by calculating the amount of fluid that is expelled through sweat during exercise. Sweat rate is specific to the discipline being tested, so athletes should conduct this test for swimming, biking and running.


Athletes should void all urine, then weigh-in wearing little to no clothing, in order to obtain the most accurate reading.

  1. Following the weigh-in, an athlete should exercise for at least one hour while keeping track of the quantity of water he or she consumes.

  2. After exercise, the athlete should towel off, and step onto the scale again, making sure to wear exactly what was worn before.

  3. The athlete’s weight before and after exercise, as well as the amount of fluid that was consumed during the exercise, will be used to determine the athlete’s sweat rate.

  4. Subtract the post-exercise weight from the pre-exercise weight in pounds or kilograms, and convert the difference to ounces of fluid loss.

  5. Then add to that number the amount of milliliters of fluid that were consumed during the exercise. This will determine how much sweat was lost during exercise.

  6. Divide the sweat loss by the duration of the exercise to determine total fluid loss during exercise.

It is best if no food, or semi-solid fueling products are consumed when checking sweat rate, and that the athlete is hydrated prior to conducting the test.

SWEAT RATE CALCULATOR This works best if converted into kilograms (kg) and milliliters (mL):

A. Body Weight pre-exercise ___________________ [lb/2.2&= kg]

B. Body Weight post exercise ___________________ [lb/2.2&= kg] (A-B)

C. Change in Body Weight ___________________ grams [kgx1000=g]

D. Volume of fluid consumed ___________________ mL [ozx30=mL]

E. Sweat Loss ___________________ mL [ozx30=mL] (C+D)

F. Exercise time ___________________ [min or hr]

G. Sweat Rate ___________________ [mL/min or mL/hr] (E/F)

The final number (G) is your sweat rate, or the amount of fluid that you lose through sweat during a specific amount of exercise (usually expressed at liters per hour). This should help you determine the amount of fluid you should be drinking during and after your workouts.


  • Sweat rates generally increase after 10–14 days of heat exposure, so sweat rate should be calculated following heat acclimatization.

  • Higher sweat rates are generally found in men and those that are highly fit.

  • Temperature plays a role in sweat rate, so calculations should be done for different environments (winter vs. summer OR hot vs. cold spaces).

  • When first beginning an exercise routine in heat, your body loses more sodium through sweating, so slightly increase the amount of sodium in your diet until you’ve become adapted (after 10–14 days).

That is it, that is all there is to it. Keep in mind, that when you hydrate, you should not just drink water, especially if you are training/racing endurance events. Electrolytes must be replenished! Happy training, racing season has already begun, hope to see you out there.

Richard Nevarez

Ironman Certified Coach

FE26TriCoach, LLC

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